1. Field of the Invention
The present invention relates to a compensation apparatus for feedback positions of an encoder and a method for operating the same, and more particularly to an on-line compensation apparatus for feedback positions of an encoder and a method for operating the same.
2. Description of Prior Art
With the development of science and technology, the precision, high-speed, high-resolution, and high-bandwidth systems are considered as major objectives in modern industries. The speed or position control is required for many products and equipment with motors, such as optical disk drivers, printers, X-Y platforms, robot arms, semiconductor processing equipment, and so on. Once the speed and position can be accurately controlled, the large improvement in performance can be attained. Accordingly, the accurate control is more and more important in modern science and technology.
In the servo control system, the position and speed control are implemented by feeding back the position and speed information of the motor to the driver. The high-resolution position and speed feedback signals are required to achieve the accurate position and speed control, namely, a high-resolution encoder is required.
The magnitude of the sensed signal will be varied with the rotating speed of the motor, that is, the magnitude of the sensed signal is larger when the motor rotates more slowly, and vice versa. Accordingly, the existing high-resolution encoder uses an interpolation technology to the analog A and B pulse signals with sine and cosine components. Because the orthogonal property between the phase difference of the A and B pulse signals, the mutual leading or lagging condition between the A and B pulse can be used to determine that the motor rotates in forward or in reverse, thus obtaining an absolute position at any time. In addition, the sinusoid-wave encoder has a higher position resolution than the conventional square-wave encoder. However, the A and B pulse would be influenced to produce errors due to the light-emitting or light-receiving elements, the installation of the rotating elements, or the abnormal temperature variation for long-time use. Hence, the errors of magnitude, phase, and center level of the A and B pulse tend to occur so that the calculated interpolation position will be non-ideal (including the relative position errors) to cause worse position detection.
Accordingly, it is desirable to provide an on-line compensation apparatus for feedback positions of an encoder and a method for operating the same that are applied to a motor driven to rotate at a constant speed by a driver, thus compensating the errors of feedback positions of the encoder.